In skin, Cutibacterium acnes (former Propionibacterium acnes ) can behave as an opportunistic pathogen, depending on the strain and environmental conditions. Acneic strains of C. acnes form biofilms inside skin–gland hollows, inducing inflammation and skin disorders. The essential exogenous products of C. acnes accumulate in the extracellular matrix of the biofilm, conferring essential bacterial functions to this structure. However, little is known about the actual composition of the biofilm matrix of C. acnes . Here, we developed a new technique for the extraction of the biofilm matrix of Gram-positive bacteria without the use of chemical or enzymatic digestion, known to be a source of artifacts. Our method is based on the physical separation of the cells and matrix of sonicated biofilms by ultracentrifugation through a CsCl gradient. Biofilms were grown on the surface of cellulose acetate filters, and the biomass was collected without contamination by the growth medium. The biofilm matrix of the acneic C. acnes RT5 strain appears to consist mainly of polysaccharides. The following is the ratio of the main matrix components: 62.6% polysaccharides, 9.6% proteins, 4.0% DNA, and 23.8% other compounds (porphyrins precursors and other). The chemical structure of the major polysaccharide was determined using a nuclear magnetic resonance technique, the formula being →6)-α- D -Gal p -(1→4)-β- D -Man p NAc3NAcA-(1→6)-α- D -Glc p -(1→4)-β- D -Man p NAc3NAcA-(1→3)-β-Gal p NAc-(1→. We detected 447 proteins in the matrix, of which the most abundant were the chaperonin GroL, the elongation factors EF-Tu and EF-G, several enzymes of glycolysis, and proteins of unknown function. The matrix also contained more than 20 hydrolases of various substrata, pathogenicity factors, and many intracellular proteins and enzymes. We also performed surface-enhanced Raman spectroscopy analysis of the C. acnes RT5 matrix for the first time, providing the surface-enhanced Raman scattering (SERS) profiles of the C. acnes RT5 biofilm matrix and biofilm biomass. The difference between the matrix and biofilm biomass spectra showed successful matrix extraction rather than simply the presence of cell debris after sonication. These data show the complexity of the biofilm matrix composition and should be essential for the development of new anti- C. acnes biofilms and potential antibiofilm drugs.
Halloysite nanotubes (HNTs) with surface-immobilized silver (Ag) nanoparticles (NPs) are explored as nano-templates for the surface-enhanced Raman scattering (SERS). The structure and plasmonic properties of HNTs/ Ag nanocomposite during storage in water are checked by means of the transmission electron microscopy and optical absorption spectroscopy, respectively. A remarkable SERS response is observed for and the SERS activity of HNTs/Ag stored in water for 1 week decreases by several times. The observed SERS-activity is explained by desired morphology of Ag NP distribution on the surface of HNTs, which is modified during storage in aqueous medium. The revealed SERS activity of HNTs/Ag nanocomposites seems to be promising for their application in biosensorics.
The importance of the impact of human hormones on commensal microbiota and microbial biofilms is established in lots of studies. In the present investigation, we continued and extended the research of epinephrine effects on the skin commensal Micrococcus luteus C01 and its biofilms, and also the matrix changes during the biofilm growth. Epinephrine in concentration 4.9 × 10–9 M which is close to normal blood plasma level increased the amount of polysaccharides and extracellular DNA in the matrix, changed extensively its protein, lipid and polysaccharide composition. The Ef-Tu factor was one of the most abundant proteins in the matrix and its amount increased in the presence of the hormone. One of the glucose-mannose polysaccharide was absent in the matrix in presence of epinephrine after 24 h of incubation. The matrix phospholipids were also eradicated by the addition of the hormone. Hence, epinephrine has a great impact on the M. luteus biofilms and their matrix composition, and this fact opens wide perspectives for the future research.
Halloysite nanotubes (HNTs) with immobilized gold (Au) and silver (Ag) nanoparticles (NPs) belong to a class of nanocomposite materials whose physical properties and applications depend on the geometry of arrangements of the plasmonic nanoparticles on HNT’ surfaces. We explore HNTs:(Au, Ag)-NPs as potential nano-templates for surface-enhanced Raman scattering (SERS). The structure and plasmonic properties of nanocomposites based on HNTs and Au- and Ag-NPs are studied by means of the transmission electron microscopy and optical spectroscopy. The optical extinction spectra of aqueous suspensions of HNTs:(Au, Ag)-NPs and spatial distributions of the electric fields are simulated, and the simulation results demonstrate the corresponding localized plasmonic resonances and numerous “hot spots” of the electric field nearby those NPs. In vitro experiments reveal an enhancement of the protein SERS in fibroblast cells with added HNTs:Ag-NPs. The observed optical properties and SERS activity of the nanocomposites based on HNTs and plasmonic NPs are promising for their applications in biosensorics and biophotonics.
Anodic etching of n-type {111} silicon in ionic liquid (IL) systems ([RMIM][X], R = H, Bu; X = BF -, PF -), realized under galvanostatic conditions and room temperature, allowed the formation of porous silicon surfaces with different pore morphology depending on the etching time, current density and the IL used. The study of the effect of water content in IL on the etching process has shown water content of 1% to be optimal. The role of the anion on the etching process was elucidated using 1methylimidazolium tetrafluoroborate ([HMIM][BF 4 ]) and 1-methylimidazolium hexafluorophosphate ([HMIM][PF 6 ]) IL systems. [HMIM][BF 4 ] was found to be most efficient for the formation of silicon nanostructured array with a pore size of 30-80 nm. The thus prepared porous silicon samples show fluorescence in blue light (475 nm). The NMR spectra of [HMIM][BF 4 ] ionic liquid before and after etching does not show
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